need help installing ac/only thermostat

15 years ago

We moved into this house almost a year ago. At the time the central AC didn't work; squirrels had chewed through the wiring in the attic. We eventually (after many headaches) got it replaced; however, the thermostat one company installed made a continuous clicking sounds. Another company removed it and promised to replace it but never showed up to do it.

So now I want to install one myself. The last guys removed the clicking thermostat and left the wires sticking out from the wall, so I don't know which wire went to which connection. There are three wires. I have installed a programmable thermostat to the furnace in our old house, so I have an idea what I'm doing, but I'm paranoid about blowing the transformer.

Any help greatly appreciated, as it's going up to 92 today and I'd like to get this done asap! TIA.

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Comment (1)

mr_havac
15 years ago
The 3 wires sticking out of the wall connect to terminals on the subbase marked R,Y and G. Not knowing the colors of your wires you will have to go up to the air handler and find the low voltage terminal strip which will have these (and several other)wires attached to it and note what color is attached to what terminal. IE: red to R, green to G etc. Now connect the wires to the ternimals on the tstat the same way. Make sure unit is shut off for all of this. Now the wire connected to Y on the terminal strip, (which is the cooling circuit) should have another wire connected to it and that goes down to the condenser. Another wire going to the same place should be connectd to a terminal labeled C. Incidentally, the wire connected to Y at the tstat may not be connected to a terminal in the air handler at all. It might just be connected with a wire nut to the wire that goes out to the condenser. Depends on your particular brand of unit and how it was installed. And no don't reply with the brand you have, I'm not an encyclopedia! :-) If all goes well the unit will run, if not and you're lucky it won't run and nothing will happen. If you're unlucky it won't run but might short something out that could cost you alot more then the cost of having somebody else come and hook it up. Do you feel lucky? Just out of curiosity why in the world did you have the idiot remove the other thermostat if he didn't have one to replace it with right way? Considering it's gonna be a hot one today I bet that clicking wouldn't have been no where near as annoying today providing the house was nice and cool right? Oh well, hope this helps without being to confusing, and good luck if you try. JB
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I don't understand why the thermostat has no Y connection. I don't think this is causing the problem, but it may be a an issue when you us the AC. If R and Rc are connected to the same transformer then you could have left the jumper in place and use one wire. Try disconnecting the black from Rc and putting in the jumper. Electrically is should not matter but this extra wire may be introducing some intermittent problem. If that does not work then repeat using the black wire and removing the red. Do you have a voltmeter? Measure the voltage between R/Rc and C and see if you have 24 volts. Do this when this furnace is off and if you can when the furnace is running. You may be experiencing a voltage drop which could be causing the issue. Perhaps the thermostat is detecting this as a power failure which may cause a reset condition.
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need help installing ac/only thermostat

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mr_havac

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